Apparatus for providing gravity flow in flooded coil refrigeration systems



Aug. 4, 1953 w. G. CARTTER ETAL 2,647,377

APPARATUS FOR PROVIDING GRAVITY FLOW IN FLOODED COILVREFRIGERATION SYSTEMS Filed Jan. 24, 1949 J, mam/w EWELL,

mmvrom. HUEBNER, BEEHL ER, WORREL.

HERZ/G l CALDWELL. By ATTORNEYS.

WILLIAM G. CAPTTEP, I

Patented Aug. 4, 1953 APPARATUS FOR PROVIDING GRAVITY FLOW 'IN FLOODED COIL REFRIGER- ATIION SYSTEMS William GfCartter and Joseph Richard Ewell, Monrovia, Calif., assignors to Day & Night Manufacturing Company, Monrovia, Calif., a

corporation of California Application January 24, 1949, Serial No. 72,372

Our invention relates to.a method and an apparatus for providing a gravity flow of liquid refrigerant in a flooded coil refrigeration system. It will be understood from the following description that our invention is applicable to a great many uses, but it was developed in connection with water coolers, is particularly advantageous therein because of more accurate temperature control and a higherrate of heat transfer, and will, therefore, be explained in connection therewith. This is by Way of illustration of how the method may be practiced and how the system may be used and not by way of limitation.

Most modern refrigerating units comprise, in combination, a compressor adapted to compress a refrigerant, such as Freon and to pump' such compressed refrigerant into asuitable heat'exchange unit so that the heat of compression may be removed therefrom by a circulation of air or other suitable means, a receiver or storage tank adapted to receive the cooled compressed refrigerant, and an expansion valve adapted to regulate the flow of refrigerant into a refrigerating or expansion coil.

The pressure existing in the refrigerating coil is much lower than in the receiver so that the refrigerant tends to boil and evaporate under reduced pressure and because of the latent heat of vaporization, reduces the temperature of the refrigerating coil to such an extent that considerable quantities of heat are removed from whatever medium surrounds the refrigerating coil.

In the event that all or substantially all of the refrigerant vaporizes and becomes a gas,

the efficiency of the coil is lowered because of a lower rate of heat transfer due to a gas to metal contact. It is therefore desirable to maintain as much of the refrigerant in the liquid state as possible. This is accomplished in a flooded coil system. However, the flooded systems known to the prior art required excessive quantities of refrigerant to effectively operate.

It is an object of our invention to provide a flooded coil system of refrigeration to maintain a high rate of heat transfer wherein relatively small quantities of refrigerant are required.

Flooded coil systems as heretofore known have required excessively large liquid receivers on the condensing unit to provide sufficient pump down capacities.

It is also among the objects of our invention to provide a flooded coil refrigeration system permitting the use of a relatively small liquid receiver 0. the n ens g uni 8Claims. (Cl-62-126) :by' into the expansion coil.

A further advantage of our invention lies in the fact that greater efliciency of heat exchange exists between a liquid and the metal coil than between a gas and a metal coil. It is, therefore,

a further object of our invention to provide a system of refrigeration having a higher degree .of efficiency of heat exchange or transfer between the refrigerating coils and the refrigerant.

In substantially all compressor type refrigerating systems oil used in the compressor will find its way into the refrigerant and be carried there- In a flooded type system the oil, where Freon is used, floats on the liquid refrigerant in the refrigerant receiver or header. It is essential that this refrigerating oil finds its way back into the compressor, otherwise: too high a-' percentage of non-heat absorbing liquids would remain in the evaporator of the refrigerating system.

It is a further object of our invention to provide means in a flooded coil system adapted to return the oil floating on the refrigerant back to the compressor.

A further object of our invention is to provide a new method maintaining a thermosiphonic flow in a flooded coil refrigerating sys-- tem.

Other-and further objects and advantages of our invention will become apparent from the drawings and the specifications relative thereto.

In the drawings:

Figure 1 is a sectional elevation of an apparatus =embodying theprinciples of our inven tion.

Figure 2 is an enlarged sectional elevation showing some of the details of the apparatus shown in Figure 1.

Figure 3 is a view taken on line 3-3 of Figure 2.

Figure 4 is a sectional view of a refrigerant orifice taken on line 4-4 of Figure 2.

Figure 5 is a sectional view of a modified form of a refrigerant orifice.

As illustrated in Figure 1, a complete refrigerating unit employing the principles of our invention comprises a compressor II], a heat exchange unit II, a storage tank or receiver l2, anexpansionvalve I3 and the refrigerating unit, designated generally I4, the details of which will be explained in connection with Figure 2. A temperature responsive bulb I5 is placed adjacent a return" conduit "I6 so that the temperature of the return conduit l6 will affect the bulb l5. The bulb i5 is in communication with the expansion valve jl3 by means of a capillary tube I and is adapted to control said expansion valve in 3 response to the temperature of the return conduit I6. It will be readily understood that suitable piping, such as conduits l8 and I8, is employed to complete the system.

As will be seen in Figure 2, we have illustrated our refrigerating unit in connection with a water tank 28 having a top and bottom 28a and 201), respectively, and having an inlet 2| and a discharge 22, the discharge 22 being at, the bottom so that the warmest water enters at the top.

A liquid refrigerant receiver or header 25 is positioned against the top 28in: of the water cooler 28 in gas-tight relation and is adapted to receive liquid Freon through a conduit 25 from 4 the expansion valve |3 into the chamber 25a defined by said header 25 and said top 29a. The header 25 is formed with an aperture 21 adapted to receive in fluid-tight engagement by any suitable means, such as welding, a downwardly extending sleeve 28. The sleeve 28 is formed with a reduced diameter at the lower end 29 defining an aperture 38. A conduit 3| having an external diameter substantially less than the internal diameter of the sleeve 28 is disposed through the sleeve 28, thereby defining an an? nular chamber 32. As will become apparent from a further description of our invention, it. is highly desirable, although not essential, that the volume of the annular chamber 32 exceed the volume of the conduit member 3|. The upper end of the conduit extends upwardly into the header 25 and is formed with an annular flange 33 having an external diameter greater than the diameter of the aperture 21.

The conduit 3| is also formed with a plurality of apertures 35 adjacent the lower end of the sleeve 28, which said apertures are adapted to elfect a communication between the interior of the conduit 3| and the annular chamber 32.

The conduit 3,| comprises an extension of a refrigerating coil 40. The refrigerating coil 48 is helical-wound and progresses upwardly to terminate in a straight vertical section 4 l. which said section extends through the header 25 in fluid-tight engagement above the level ofliquid refrigerant 42.

An overflow pipe 43, is positioned adjacent the top of the straight section 4| and is formed with a notch 44, the purpose of which will become apparent later. The overflow pipe 43 extends through the, Wall of the header 2-5 downwardly and communicates with the lower end of a super-heat coil 46. The coil 45 is also helicale wound on a larger diameter than the coil 40 and progresses upwardly into communication with a vertical discharge section 48, the discharge sec-- tion 48 being in communication with the return QQnduit, 1

In the operation of our refrigerating system, Freon is compressed in the compressor passes into the heat exchanger H where the heat of ee znression s r mov d b radiation 9 eth su abl m ans ther y r ni he as i e. iu-id and t en pass t e r e er 3;:

pon op in the expans on alve i3, und r ompressi n n th re er dre s throu h he cond t i a d s. disc a d the header i id Freon a sthrou h the. on uit 3i sti tli i to. a point ad a en the ap rture .5 which nermit part of. t e. li uid e n to ass. nto the W- buiar memb r .8- Sinc the tubular," m mbe 2 mmed ate con a with we 3; c is i conta n d he upp r pa of the oo r fi l: an

4 which is at a temperature sufficiently high to cause boiling, part of the Freon would be converted to gas, thereby causing Freon foam (Freon gas and liquid mixture) to rise upwardly through the. annular chamber 32 into the header 25 because of the difference in specific gravity between the foam and the liquid. The balance of the Freon contained in liquid form in the conduit 3| w ll pass, due to its weight, downwardly into the coil 48, which due to the fact that it is in contact with water, will absorb heat by means of conduction through the coil 48 to cause a boiling or gasificationof part of the liquid Freon. In view of the fact; that the coil progresses upwardly the fact that the Freon foam is lighter in Weight than the liquid Freon, the Freon foam rise thrql gh the coil 48 to the pipe 4| and heel; into the header 25.

It will be readily apparent that due to the fact that both open ends of the coil 48 are in communication with the interior of the header 25, the pressure on both ends is equal; that, therefore, circulation through the coil 4.0 is caused solely by the differential in specific. gravity between the liquid Freon entering the conduit 3| and the foam circulating upwardly through the coil 48. It, therefore, becomes apparent that it is essential to the satisfactory operation of our system that, Freon remain in the liquid state until it has entered the bottom of the coil 48. In order to accomplish this, some means must be provided for insulating the conduit 3| from the heating effect of the water contained in the tank 20. This is accomplished by means of the sleeve 28 and the Freon orifices. 35. Some of the liquid Freon passes through the orifices into the annular chamber 32 where it absorbs heat by conduction through the walls of the sleeve 28 from the surrounding water and, again, due to the difference in specific gravities between the liquid Freon and Freon in the gaseous state, the evaporating Freon percolates upwardly, thereby carrying the absorbed heat along with it.

After the Freon has. risen in the form of a lightweight foam through the annular chamber- 32 and throu h the coil 48 back into the header 25, it. then passes into the over-flow pipe 43, into a Supcreheat coil 46 wl-iich is in communication with the compressor ill and through the conduits 4g and E5 Circulation through the coil 46 is Certifi d, both by the differential in specific gravity between the foam Freon and gaseous Freon and by the diiferentialin pressure between the header 2 5 and the intake of the compressor It. By proper designing and regulation of the pressure at the-intake of the compressor in, the coil 48 may maintained substantially wet throughout its entire trayereq until it enters the conduit 15 the cycle of operation is again repeated. I Whereas, we have shown the inlet to the coil 4% beil'il; g vitationally lower than the discharge from the coil to. the compressor, such is necessary only in the eventv that. it is desired to maintain a wet surface at all times in the superheat, coil 48. In View of the fact that, the surface of the coil 46 is small with respect to. the surface of the coil 48, it. is, not essential to maintain the coil a wet wall condition. As a matter of fact, it. may be desirable to design the equipment so that, the coil 46: will be substantially dry in order to obtain adequate super heat to effectiyely operate the remote bulb and control the. liquid l e s.

wh reas. we have, lus r ted th nlet to. the super-heat coil 48 as being formed with. a V- shaped notch 44, it should be understood that other configurations, such as cutting the pipe 43 obliquely, will work equally satisfactorily. The purpose of such an inlet is to aid in removing oil which may be floating on the liquid refrigupward in a flooded coil refrigerating system with the use of relatively small quantities of refrigerant, said method comprising the steps of introducing liquid refrigerant into a closed receptacle, discharging said refrigerant into a vertical tube which communicates with the lower end of an expansion coil andpreventing absorption of heat in the refrigerant while in the vertical tube so that boiling of the refrigerant takes place only in the expansion coil whereby it is caused to move upwardly due to gravity displacement by liquid refrigerant in the vertical tube. We have also provided a method for preventing the absorption of heat in the above mentioned vertical tube by passing a portion of the liquid refrigerant into an annular chamber around the outer surface of said tube so that the refrigerant contained in said annular passage is caused to boil and carry heat upwardly with the refrigerant foam resulting from said boiling. l

We have shown in Figure a modification of what has been termed the Freon orifice; that is, communication between the lower end of the conduit 3i and the annular'chamber 32. In this modification, we have terminated the conduit 3| at a point spaced above the entry to the coil 40 ed to control the expansion valve l3 by means of the capillary tube Ilia. It will also be understood that any suitable or standard pressure regulating switch may be employed, such as between the receiver and a source of power driving the compressor to prevent too high a pressure in the receiver l2.

While we have herein shown and described our invention in what we have conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope of our invention, which is not to be limited to the details disclosed herein, but is to be accorded the full scope of the claims so as to embrace any and all equivalent methods and devices.

Having described our invention, what we claim as new and desire to secureby Letters Patent is:

1. A refrigeration expansion coil unit having an inlet in communication with an expansion valve and an outlet in communication with a compressor, said unit having a cooling coil and a superheat coil and a header comprising a liquid refrigerant receiver adapted to receive liquid refrigerant from said expansion valve, said cooling coil having a relatively straight section depending from the lower portion of said header and in communication with a helical-wound upwardly pro gressing coil, which said helical coil terminates inside said header at a point above liquid refrigerant contained therein, insulating means adapted to prevent boiling of refrigerant in said straight section, said means comprising a sleeve of greater diameter defining an annular chamber between said straight section and said sleeve, means in the lowermost portion of said straight section defining a communication for liquidre- ,frigerant from said section into said annular chamber and means defining a communication between said annular chamber and said header adjacent the bottom of said header, whereby liquid refrigerant passes from said-straight section into said annular chamber and is caused to boil by the absorption of heatfrom a medium surrounding said sleeve and to carry said heat upwardly by convection currents into said header, said cooling coil having a discharge in said header above the level of liquid refrigerant contained therein, said superheat coil having an inlet in said header above the level of said liquid refrigerant, a relatively straight section connecting said inlet with the lowermost portion of said superheat coil, said superheat coil .being helical-wound and upwardly progressing and having a discharge in communication with the discharge of said expansion refrigeration unit.

'2. In a flooded coil refrigeration system having a header adapted to receive liquid refrigerant and an expansion coil comprising a depending leg in communication with the interior of said header, and a spiral coil communicating between the bottom of said leg and the interior of said header forming a loop, means for inducing the thermo-siphonic circulation of refrigerant through said expansion coil, said means comprising a sleeve surrounding said depending leg closed at the bottom and spaced therefrom defining therebetween an annular chamber in open communication with said header, said depending leg of said expansion coil being formed with apertures adapted to permit communication of liquid refrigerant from the lowermost extremity of said depending leg into said annular chamber, whereby heat being absorbed by the surface of'said sleeve-is absorbed by said liquid refrigerant in said annular chamber and carrier upwardly into said refrigerant receiver. I

3. In a flooded coil refrigeration system a header adapted to receive the liquid refrigerant, an expansion coil comprising a vertical leg in communication with the lowermost portion of said header and a substantially vertically disposedloop in communication with the interior of said header, means for inducing a thermo siphonic action through'said expansion coil, said means comprising a sleeve disposed, around and spaced from said vertical leg defining an annular chamber enclosed at the bottomand in open communication with said refrigerant header, and

means adjacent the lower extremity thereof communicating with the interior of said vertical leg whereby liquid refrigerant in said vertical leg flows into said annular chamber to absorb heat and to carry said heat upwardly to thereby prevent the absorption of heat in said vertical leg.

4. In a flooded coil refrigeration system the combination of a liquid refrigerant header, an expansion valve adapted to control the flow of liquid refrigerant into said header, an expansion coil comprising a loop of conduit having a depending leg in communication with the interior of said header and an upwardly extending loop also having one end in communication with the interior of said header, means for inducing a thermo-siphonic circulation of refrigerant through said loop, said means comprising a sleeve disposed around and spaced from said depending leg defining an annular chamber therebetween, said sleeve being secured to said leg at the lowermost extremity thereof to form a fluid tight closure for said chamber, said chamber being in open communication with said refrigerant header, said dependent leg being formed with apertures adapted to communicate liquid refrigerant into said annular chamber adjacent the bottom thereof whereby heat absorbed by said sleeve will be carried upwardly by evaporation of said refrigerant in said chamber.

5. In a flooded coil refrigeration system the combination of a liquid refrigerant header, an expansion valve adapted to control the flow of liquid refrigerant into said header, an expansion coil comprising a loop of conduit having a depending leg in communication with the interior of said header and an upwardly extending loop also having one end in communication with the interior of said header, means for inducing a thermo-siphonic circulation of refrigerant through said loop, and liquid level means for maintaining a substantially constant liquid level in said header, said liquid level means comprising a super heat coil having one end in communication with the interior of said header adapted to return gaseous refrigerant to a. suction line of said system and means responsive to temperature of said returning gaseous refrigerant for actuating said expansion valve.

6. In a flooded coil refrigeration system the combination of a liquid refrigerant header, an expansion valve adapted to control the flow of liquid refrigerant into said header, an expansion coil comprising a loop of conduit having a depending leg in communication with the interior of said header and an upwardly extending spiral loop also having one end in communication with the interior of said header, means for inducing a thermo-siphonic circulation of refrigerant through said loop, said means comprising a sleeve disposed around and spaced from said depending leg defining an annular chamber therebetween, said sleeve being secured to said leg at the lowermost extremity thereof to form a fluid tight closure for said chamber, said chamher being in open communication with said refrigerant header, said dependent leg being formed with apertures adapted to communicate liquid refrigerant into said annular chamber adjacent the bottom thereof whereby heat absorbed by said sleeve will be carried upwardly by said refrigerant in said chamber, and means for maintaining a substantially constant liquid level in said header, said last mentioned means comprising a super heat coil having one end in communication with the interior of said header adapted to return gaseous refrigerant to a suction line of said system and means responsive to temperature of said returning gaseous refrigerant for actuating said expansion valve.

7. In a fllooded coil refrigeration system the comb -"on of a liquid refrigerant header, an

expansion valve adapted to control the flow of liquid refrigerant into said header, an expansion coil comprising a loop of conduit having a depending leg in communication with the interior of said header and an upwardly extending spiral loop also having one end in communication with the interior of said header and terminating above the normal level of said liquid refrigerant, means for inducing a thermo-siphonic circulation of refrigerant through said loop, said means comprising a sleeve disposed around and spaced from said depending leg defining an annular chamber therebetween, said sleeve being secured to said leg at the lowermost extremity thereof to form a fluid tight closure for said chamber, said chamber being in open communication with said re frigerant header, said dependent leg being formed with apertures adapted to communicate liquid refrigerant into said annular chamber adjacent the bottom thereof whereby heat absorbed by said sleeve will be carried upwardly by said refrigerant in said chamber, and means for maintaining a substantially constant liquid level in said header, said means comprising a super heat coil having one end in communication with the interior of said header adapted to return gaseous refrigerant to a suction line of said system and means responsive to temperature of said returning gaseous refrigerant for actuating said expansion valve.

8. In a flooded coil refrigeration system the combination including: a header adapted to receive liquid refrigerant, a first conduit communicating with said header below the refrigerant level therein and extending steadily downward from said header, a second conduit joined t said first conduit at the lower end of said first conduit, the other end of said second conduit communicating with said header, and a sleeve surrounding said first conduit communicating at its upper end with said header and closed at its lower end, thereby forming an annular space surrounding said downwardly extending conduit, said downwardly extending conduit having an aperture communicating with said annular space.

WILLIAM G. CARTTER. J. RICHARD EWELL.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,923,170 Slagel Aug. 22, 1933 2,035,710 Leyner Mar. 31, 1936 2,067,431 Albertson Jan. 12, 1937 2,094,565 Wolfert Sept. 28, 1937 2,133,959 Buchanan Oct. 25, 1938 2,193,696 Ramsaur Mar. 12, 1940 2,450,735 Millet Oct. 5, 1948 OTHER REFERENCES Audels Refrigeration and Air Conditioning Guide, Theodore Audel and Company, Publishers, 49 West Twenty-third Street, New York 10, New York, copyright, 1944. 

